Satellite communication (SATCOM) has made wireless local area networks (LAN) ubiquitous in a true sense. SATCOM requires the use of high-gain antennas due to its long communication distance. The conventional SATCOM system uses a large dish antenna that can be mechanically controlled to change a beam direction. Planar antennas that can replace dish antennas have been developed. However, mechanical beam control is still required to establish a link between satellite and ground stations.
Phased arrays are very attractive for satellite communications due to their planar structure and agile electronic beam control. There are several approaches to electronically control a beam. The majority of today's phased arrays rely on phase shifters to steer a beam. Although there have been many efforts for cost and size reduction, the phase shifter is still one of the most expensive parts in the SATCOM ground station system. The use of heterodyne scanning eliminates the need for phase shifters. However, the heterodyne scanning technique requires complex local oscillator (LO) networks, making the technique far from practical.
Moreover, beam steering for these approaches requires a priori knowledge of the satellite location or a feedback system to track the satellite using its beacon signal. This is a problem especially when the ground station is on the move. The ground station needs to continuously adjust the elevation and azimuth angles of radiation using peak-search of the beacon signal.
Smart antennas use digital beam-forming (DBF) techniques to overcome this problem, but this requires power-hungry analog-to-digital converters and digital signal processor circuits. Therefore smart antennas are not suited for SATCOM where the array requires a large number of elements. Needs exist for improved satellite communication systems.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings.